Heat Exchange System and Method

ABSTRACT

A dual fluid heat exchange system is presented that provides a stable output temperature for a heated fluid while minimizing the output temperature of a cooled fluid. The heated and cooled fluids are brought into thermal contact with each other within a tank. The output temperature of the warmed fluid is maintained at a stable temperature by a re-circulation loop that connects directly to the mid portion of the tank such that the re-circulated fluid flow primarily warms only a re-circulation section of the tank. The other, lower flow rate, section of the tank may be positioned so that it has a cooler temperature and thus serves to increase the efficiency of the heat exchange by extracting extra heat energy out of the cooled fluid before it leaves the tank. Alternatively, the low flow rate section of the tank may be warmer than the re-circulated section, and thus allow the re-circulated section to be cooler than the output temperature of the warmed fluid.

CROSS-REFERENCE TO CO-PENDING APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/383,868 entitled “Heat Exchange System and Method” that was filed onApr. 15, 2019 and issued on Aug. 17, 2021 as U.S. Pat. No. 11,092,382and was a continuation of U.S. patent application Ser. No. 15/668,908entitled “Heat Exchange System and Method” that was filed on Aug. 4 2017and issued on Apr. 16, 2019 as U.S. Pat. No. 10,260,825, and was acontinuation of U.S. patent application Ser. No. 13/963,158 entitled“Heat Exchange System and Method” that was filed on Aug. 9, 2013 andissued on Aug. 8, 2017 as U.S. Pat. No. 9,726,443, and was a divisionalapplication of U.S. patent application Ser. No. 12/395,173 entitled“Heat Exchange System and Method” that was filed on Feb. 27, 2009 byWalter Deacon and Timothy Parbs, and issued on Sep. 10, 2013 as U.S.Pat. No. 8,528,503, the contents of which are herein all incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to heat exchange systems, and moreparticularly to a heat exchange system and method by which a first fluidis efficiently warmed to a consistent temperature by a second fluid.

BACKGROUND OF THE INVENTION

Heat exchange systems have been used for different purposes, such aswarming water used for domestic, commercial, or industrial purposes.Designers of heat exchange systems have faced many challenges such aslimitations on the size of the heat exchanger. Additionally, there is aneed for the warmed fluid to exit the system at a consistenttemperature. Managing the temperature of the cooled fluid leaving thesystem is also a challenge facing heat exchange systems due toefficiency and regulatory concerns.

Changes in the demand for heating require that heat exchange systems beable to provide vastly different amounts of heating, which can lead tosubstantial temperature changes in the output of the warmed fluid.Conventional methods of stabilizing the output temperature of the warmedfluid often rely on adjusting the flow rate of the fluid to be cooled.Although this approach may reduce the variability of the warmed fluidoutput temperature, the cooled fluid temperature leaving the heatexchanger can vary drastically.

Conventional systems used to heat water often have two fluid circuits.Typically water to be heated circulates in the first fluid circuit in aliquid state while steam circulates in the second fluid circuit attemperatures that are often above the boiling point of water. Bothcircuits meet at a heat exchanger unit where the cool water is warmed byflowing over thermally conductive conduits containing the hightemperature steam. The water exits the heat exchanger in a heated state,and if the demand for hot water increases, the flow rate of the hotwater vapor is simply increased.

In conventional systems, the temperature of the heated water at theoutlet varies based on the outgoing water flow rate variations and/oraccording to incoming water temperature variations. As a result of thevariable flow rate through the heat exchanger, the quantity of energytransmitted cannot be precisely controlled causing the temperature ofthe output water to vary. Additionally, the high temperature of thesteam limits control, but is needed for high usage situations. In lowusage situations, the steam will often warm the water up to atemperature beyond that which is desired.

A varying output temperature of the cooled fluid from the heat exchangercan reduce the efficiency of the energy exchange since energy remainingin the cooled fluid is often wasted. There are also many instances wherethere are requirements and regulations on the temperature of the cooledfluid leaving the heat exchanger. In systems where the cooled fluid isnot returned to its source for reheating, the cooled fluid is oftendumped into a sewer system or waterway. In addition to beinginefficient, dumped fluids often must be below a specified temperatureto avoid damaging sewer systems or to avoid causing thermal pollutionthat can lead to problems such as algae blooms.

In addition to the other problems associated with heat exchangers, floorspace is often at a premium in modern mechanical rooms so it isdesirable to have a heat exchanger with a minimal footprint. The costdifference in using a system with a small 1.75 square yard footprintversus having to stack multiple regular horizontal exchangers can bethousands of dollars. Thus, it is desirable to provide a verticallyoriented heated exchanger with a minimal footprint. Additionally,retrofit applications require heat exchangers to be placed in smallareas. Large, bulky 40 to 50 year old exchangers may be at the end oftheir useful life. Many times a facility is built up around thesefailing units and replacing them with a similarly sized unit wouldentail major demolition. Vertical exchangers can be wheeled through adoorway and they can be piped up with the existing unit in place,causing minimal downtime. Sometimes the existing unit is encapsulatedand left in place.

Attempts have been made to solve some of these problems, such as in U.S.Pat. No. 6,857,467 issued to Lach, the contents of which are hereinincorporated by reference. The Lach patent claims to disclose a “heatexchange system . . . used for heating a first fluid with a second fluid[using] . . . a flooded heat exchanger . . . capable of being flooded ina determined proportion [and] . . . includes a second fluid circuitcontrol valve . . . for controlling the flow rate of the second fluid .. . whereby the proportion of the heat exchanger which is flooded . . .can be selectively calibrated. The heat exchange system also includes afirst fluid pre-heating device . . . for partly pre-heating the firstfluid before it is heated by the second fluid, whereby the first fluidtemperature at the first fluid circuit downstream end will bestabilized.” Although the Lach patent attempts to improve thetemperature stability of a first fluid leaving the heat exchanger, theLach patent fails to provide a mechanism for stabilizing and reducingthe output temperature of the cooled fluid.

Semi-instantaneous water heaters attempt to stabilize the outputtemperature of water heaters by having small mixing tanks in which waterdelivered from the heat exchanger is blended with water in the vessel.U.S. Pat. No. 4,278,069 issued to Clark discloses an example of asemi-instantaneous water heater, the contents of which are hereinincorporated by reference. While it is possible to obtain temperaturecontrol of the warmed fluid in semi-instantaneous water heaters, theoutput temperature of the cooled fluid is uncontrolled.

Although designs by Lach and Clark have attempted to solve some of theproblems associated with heat exchangers, all of these problems have yetto be fully addressed. Objects of the present invention includeproviding a fluid heater with a low installation cost, providing a moreefficient heat transfer from steam, providing a heat exchanger thatrequires less physical space, providing a heat exchanger that does notrequire a condensate pump, a vacuum breaker, or a pressure regulatingvalve station, controlling the temperature of the liquid leaving theheat exchanger within ±3° F., and decreasing the temperature of thesteam condensate leaving the heat exchanger.

SUMMARY OF THE INVENTION

A dual fluid heat exchange system is presented that provides a stableoutput temperature for a heated fluid while also minimizing the outputtemperature of a cooled fluid. The heated and cooled fluids are broughtinto thermal contact with each other in a tank. The output temperatureof the warmed fluid is maintained at a stable temperature by are-circulation loop that connects directly to a mid portion of the tanksuch that the re-circulated fluid flow primarily warms only are-circulation section of the tank. The other, lower flow rate, sectionof the tank may be positioned so that it has a cooler temperature andthus serves to increase the efficiency of the heat exchanger byextracting extra heat energy out of the cooled fluid before it leavesthe tank. Alternatively, the low flow rate section of the tank may bewarmer than the re-circulated section, and thus allow the re-circulatedsection to be cooler than the final output temperature of the warmedfluid.

The cooled fluid may be condensed in a controlled manner from a vaporform to a liquid within the tank in order to release energy to heat thewarmed fluid. A control valve downstream of the tank may be used toadjust the condensate flow rate out of the tank in order to control therelative proportion of vapor to condensate.

The two warmed fluid sections of the tank may be structured so thatthere is no barrier between them, or there may be a separator to reduceunintended mixing between the sections. The structure of the tank forbringing the warmed and cooled fluids into thermal contact may include aplurality of vertical thermally-conductive pipes and a plurality ofhorizontal plates.

The foregoing summary does not limit the invention, which is defined bythe attached claims. Similarly, neither the Title nor the Abstract is tobe taken as limiting in any way the scope of the disclosed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Each of the drawing figures now described shows an exemplary embodimentof the present invention.

FIG. 1 is a schematic view of a heat exchange system with are-circulation circuit.

FIG. 2 is a schematic view of another heat exchange system with are-circulation loop.

FIG. 3 is a schematic view of a heat exchange system with are-circulation loop that includes a storage tank.

FIG. 4 is a schematic view of a heat exchange system with are-circulation loop that draws fluid from the midsection of a tank andtransfers the fluid to an inlet line.

FIG. 5 is a schematic view of a heat exchange system with are-circulation loop and a reverse flow mechanism in a condensate outputline.

FIG. 6 is a schematic view of a heat exchange system where fluid leavesthe system from a re-circulation circuit.

FIG. 7 is a graphic representation of a high flow fluid temperaturegradient within a heat exchanger tank having a re-circulation loop.

FIG. 8 is a graphic representation of a low flow fluid temperaturegradient within a heat exchanger tank having a re-circulation loop.

FIG. 9 is a cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes extending between avapor inlet and a vapor condensate outlet.

FIG. 10 is another cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes extending between avapor inlet and a vapor condensate outlet.

FIG. 11 is a cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes and a dividerbetween a pre-warming section and a re-circulation section.

FIG. 12 is another cross-sectional view of a heat exchange tank having aplurality of vapor-vapor condensate containing pipes and a dividerbetween a pre-warming section and a re-circulation section.

FIG. 13 is a cross-sectional view of a heat exchange tank having aplurality of horizontally oriented vapor-vapor condensate containingplates.

FIG. 14 is another cross-sectional view of a heat exchange tank having aplurality of horizontally oriented vapor-vapor condensate containingplates.

FIG. 15 is a cross-sectional view of a heat exchange tank having aplurality of densely packed horizontally oriented vapor-vapor condensateplates.

FIG. 16 is another cross-sectional view of a heat exchange tank having aplurality of densely packed horizontally oriented vapor-vapor condensateplates.

FIG. 17 is a cross-sectional view of a heat exchanger tank having abrazed plate construction where two fluids flow on alternating levels inopposite directions.

FIG. 18 is another cross-sectional view of a heat exchange tank having abrazed plate construction where two fluids flow on alternating levels inopposite directions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention may be used with any type of heat exchanger and isparticularly suited for use with domestic hot water systems, ammoniabased refrigeration systems, heating water/glycol building heat systems,oil or heat transfer fluid systems, wash stations, and emergencyshowers. However, for descriptive purposes, the present invention willbe described in use with a heat exchanger heating water with hot steam.

FIG. 1 shows a circuit diagram of a heat exchange system with a heatexchange tank 10. A water circuit connecting to the heat exchange tankhas a water input line 15 for inputting cool water into the tank at acool water input 20 on the tank, and a water output line 25 withdrawingheated water from a hot water outlet 30 on the tank. A stabilizationcircuit with a re-circulation line 35 and a re-circulation pump 40diverts a portion of the heated water leaving the tank back into thetank at a re-circulated water inlet 45 to stabilize the temperature ofthe water leaving the tank. The re-circulation pump may be a variablespeed pump so that the flow rate through the recirculation line may beadjusted based on the temperature of the water in the tank and/or theflow rate of water into and out of the system.

A vapor circuit includes a steam input line 50 that provides hot steamto the heat exchange tank 10 at a steam inlet 55 on the tank. A driptrap 60 may be connected to the steam input line to remove condensationfrom the steam line. Within the tank, the steam is placed in thermalcommunication with the water from the water input line. Since the steamis at a higher temperature than the water, heat is transferred from thesteam to the water causing the steam to condense into a steam condensatewhile the water is warmed. The interface between the steam and the watermay be structured in a variety of ways to facilitate heat transfer fromthe steam to the water. In one embodiment of the invention, the steam isconfined to a plurality of vertically oriented tubes extending theheight of the tank while the water to be warmed substantially surroundseach of the tubes. In another embodiment of the invention, the steam isconfined to a steam conduit close to the exterior of the tank such thatthe conduit is only partially surrounded by water and only a portion ofthe conduit is structured to facilitate thermal communication betweenthe steam and the water. In yet another embodiment of the invention, thesteam in the tank is confined to a conduit having a plurality of bafflesstructured to increase the interior surface area of the conduit andthereby facilitate heat transfer from the steam to the water. The steamand water may progress through the tank in a co-current direction, orthe steam and water may travel in a counter co-current direction suchthat the steam input is located near the water output and the waterinput is located near the condensate output.

The steam/water interface is preferably made from thermally conductivematerials such as copper (380 W/mk thermal conductivity), aluminum (200W/mk), silver, (429 W/mk), type 304, 316, or 302 stainless steel (16.2W/mk), type 410 stainless steel (24.9 W/mk), or CoolPoly® E5101Thermally Conductive Polyphenylene Sulfide (20 W/mk).

A condensate line 65 withdraws steam condensate via a condensate outlet70 in the tank. A condensed steam outlet 75 may be in the condensateline to release condensate in the event of an over pressurization. Acontrol valve 80 in the condensate line is structured to restrict theflow of condensate out of the heat exchanger tank. By limiting the flowof condensate, the steam conduit within the tank may be fully orpartially flooded with steam condensate. As a result of the condensatehaving a greater density than the steam, the condensate will sink to thelower portions of the tank thereby forming a steam/condensate partitionwithin the tank. The condensation of steam in the steam section releasesa greater amount of heat energy into the water than the cooling of thesteam condensate allowing the water near the steam to be significantlyheated relative to the water near the steam condensate. By decreasingthe temperature of condensate leaving the heat exchanger tank, theefficiency of the heat exchanger is increased. Downstream of the controlvalve 80 is a condensate trap 85 adapted to prevent the flow a steam inthe event of a control valve failure. A bleed valve may be positionednear the condensate trap to release steam in the event of anunintentional vaporization.

FIG. 2 illustrates a heat exchanger tank 10 where the re-circulatedwater input 45 is located between the hot water outlet 30 and thecondensate outlet 70 such that a pre-warming section 90 within the tankis formed between the cool water inlet 20 and the re-circulated waterinlet 45. In the water flow downstream of the pre-warming section, are-circulation section 95 is located in the heat exchange tank betweenthe re-circulation input and the hot water outlet. Within there-circulation section, the water is exposed to hot condensate andcondensing steam such that the average temperature of the water withinthe re-circulation section to be greater than in the pre-warming sectionof the tank.

In the re-circulation section of the heat exchanger tank, the water hasan average flow rate that is higher than in the pre-warming sectionbecause the water in the re-circulation section is moved by both there-circulation pump and the means that moves the water through the coolwater input line, such as a water tower. The higher flow rate of there-circulation section facilitates heat transfer from the steam byacting to reduce the likelihood that water near the steam conduit issubstantially warmer than the rest of the re-circulation section.Additionally, the higher flow rate increases mixing within there-circulation section and thereby assists in stabilizing thetemperature of the water leaving the hot water output of the waterheater tank. In one embodiment, the pre-warming and re-circulationsections are substantially equal in size. In other embodiments, onesection may be larger than the other section. In an exemplaryembodiment, the pre-warming section is between 25% and 200% the size ofthe re-circulation section.

In order to optimize heat transfer from the steam and condensate to thewater, it is desirable to structure the tank so that the steamcondensate leaves the tank at a cool temperature. Preferably, thetemperature of the water in the pre-warming section should be as cold aspossible while the water in the re-circulation section should be nearthe desired hot output temperature. Thus, the temperature gradientbetween the two sections should be maximized. In order to create anoptimal temperature gradient, the flow of water from the pre-warmingsection to the re-circulation section is preferably limited to only aflow rate similar to the flow rate out of the heat exchange system. Theheat exchanger tank may be structured to limit the unintentional flowrate. In one embodiment, the re-circulated water input is structured sothat the re-circulated water enters the re-circulation section with avelocity that moves it away from the pre-warming section. In anotherembodiment, an aperture between the pre-warming section and there-circulation section functions to limit mixing between the twosections. In yet another embodiment, the two sections have baffles thatincrease intra-sectional mixing, but decrease unintentional mixingbetween the two sections. For example, the baffles may be oriented suchthat the water re-circulation section flows in a continuous upwardspiral.

The embodiment shown in FIG. 3 includes a storage tank 100 in there-circulation loop designed to increase the total volume of water inthe loop. By storing heat energy in the storage tank from watercirculated from a first recirculation inlet 101, the system is able toefficiently store energy during low usage conditions. During high usageconditions, the water in the storage tank may be directly mixed into thewater input line 15 to warm the water before it enters the heatexchanger tank, or the water from the storage tank may be fed into there-circulated water inlet of the heat exchanger tank. If the water inthe storage tank is fed directly into the water input line 15, adiverter valve 105 in the line may be used to force a portion of thecool water to be fed into the storage tank through a bypass line 110from a second recirculation inlet 112. Upon leaving the storage tank 100the water travels to a recirculation outlet 114 and then onto the heatexchange tank 10. The diverter valve 105 is located between the secondrecirculation inlet and the recirculation outlet 114. In the illustratedexample, the water from the first recirculation inlet 101 enters thestorage tank 100 at a first tank port 103 and the water from the secondrecirculation inlet 112 enters at a second tank port 104. The waterleaving the tank exits through a third tank port 106.

FIG. 4 illustrates a heat exchanger tank where the water drawn by there-circulation pump 40 is drawn from a re-circulation outlet 115 on theheat exchange tank 10 that is separate from the hot water outlet 30 onthe tank. In the illustrated example, the water in the re-circulationline flows to the water input line 15, however in another embodiment,the re-circulated water is fed back into the tank via a separatere-circulated water inlet. In the system shown in FIG. 4, are-circulation section 95 in the tank is formed between the cool waterinput and the re-circulation output. Located downstream of there-circulation section is a post-warming section 120 where the water isfurther heated before it leaves the system through the water output line25. Since additional heating is done before the water leaves the system,the temperature of the water in the re-circulation loop can be somewhatless than the desired temperature of the water at the output.

FIG. 5 illustrates an example of a heat exchange system having a reverseflow mechanism 125 in the condensate line 65 and a lock valve 130 in thesteam input line 50 for decreasing or stopping the flow of steam intothe heat exchange tank. If the proportion of condensate to steam withinthe heat exchanger tank is below a desired amount, the lock valve canisolate the heat exchange tank from new steam. As the steam in the tankcools and condenses, a relative vacuum will form within the steamportion of the heat exchange tank. As a result of the relative vacuum,the condensate will be drawn back into the heat exchange tank. If thecondensate is warmer than the water in the heat exchange tank,additional heat energy will be transferred from the condensate to thesteam and the efficiency of the heat exchange system will be furtherincreased. The system may also include a condensate evacuation circuit(not shown) extending between the condensate line 65 and the steam inputline 50 for draining condensed steam from the steam input line.

FIG. 6 illustrates an example of a heat exchange system where the entirehot water output of the heat exchange tank 10 travels through there-circulation pump 40. The heated water output from the system is drawndirectly from the re-circulation line 35 while the water input line 15also feeds directly into the re-circulation line. In this design, there-circulation section occupies substantially the entire heat exchangetank. Due to the amount of mixing between the re-circulated water andwater from the input line, the system configuration of FIG. 6 providesheated water with an exceptionally consistent temperature. Theconfiguration of FIG. 6 is also able to maintain a consistent watertemperature during bursts of extremely high water usage.

FIG. 7 shows a representative graph of the water temperature within theheat exchanger tank 10 of FIG. 2 relative to the water's location withinthe tank during a high usage (100 gallons per minute) condition. Whenthe water enters the tank it has a relatively low temperature 135 thatincreases as the water absorbs heat from the steam condensate as itmoves through the pre-warming section. The low temperature of the waterallows the condensate temperature to also be low which increases theefficiency of the heat transfer within the tank. At or near thepre-warming/re-circulation section divide 140, the temperature of thewater jumps as it is mixed with hot re-circulated water. Once the waterenters the re-circulation section, its flow rate increases and itstemperature increase as it absorbs heat energy from the condensing steamand/or the steam condensate.

FIG. 8 shows a representative graph of the water temperature within theheat exchanger tank 10 of FIG. 2 relative to the water's location withinthe tank during a low usage (2 gallons per minute) condition. When waterenters the tank it has a relatively low temperature 135 that increasesas the water absorbs heat from the steam condensate moving through thepre-warming section. Since the water has a greater exposure time in thepre-warming section relative to the high flow conditions, the amount ofheat energy absorbed from the steam condensate is greater. As the waterenters the re-circulation section of the heat exchanger, the temperatureagain jumps as it mixes with the re-circulated water. In there-circulation section, the rate at which the temperature of the waterincreases relative to its position is less than in the high flow ratesdue to less of a temperature gradient between the steam/steam condensateand the water.

FIGS. 9 and 10 show perspective cross-sectional views of the interior ofa heat exchanger tank 10 with a steam inlet 55, a condensate outlet 70,and a re-circulated water inlet 45. The tank connects to a water inputline 15, a water output line 25, a re-circulation line 35, a steam inputline 50, and a condensate line 65. Within the tank are a plurality offloodable steam pipes 145, or conduits, extending between the steaminlet and the condensate outlet. The illustrated pipes have smalldiameters relative to the tank so that the pipes have a high surfacearea to interior volume ratio that facilitates the transfer of heatenergy from the steam or steam condensate. Additionally, the pipes arespaced apart so that the water may easily flow within the tank in orderto minimize the occurrence of local water hot spots. In the illustratedexample the pipes are substantially straight, however in otherembodiments the pipes may be curved so as to increase the path lengththat the steam/steam condensate must travel from the steam inlet to thecondensate outlet. In the illustrated example, the pipes aresubstantially uniform in their diameter, however in other examples thediameter of the pipes may be larger closer to the condensate outlet suchthat the condensate has a longer period of time to be cooled by thewater from the water input line.

In the example illustrated in FIGS. 9 and 10, the water flowing throughthe water input line 15 has a temperature of 65° F. and a flow rate of 1GPM. The water leaving the heat exchanger tank through the water outputline 25 has a temperature of 140° F. and a flow rate of 3 GPM. The waterentering the heat exchanger tank through the re-circulation line 35 hasa flow rate of 2 GPM and the temperature of the water close to there-circulated water inlet has a temperature of 120° F. The temperatureof the steam entering the tank through the steam input line is 300° F.,and the condensate leaving the tank has an average temperature of 100°F. The in the illustrated example, the average density of the waterwithin the re-circulation section is 0.98803 g/mL while the averagedensity of the water within the pre-warming section is 0.99821 g/mL suchthat the water in the re-circulation section floats on the water in thepre-warming section.

FIGS. 11 and 12 show perspective cross-sectional views of a heatexchange tank 10 with a section divider 150 between the pre-warming andre-circulation sections. The divider is structured to minimize the flowof heat energy from the re-circulation section to the pre-warmingsection while not hindering the replenishment of the re-circulationsection when hot water is drawn out of the system. In the illustratedexample a disk serves as the section divider, however other types ofdividers may be utilized. For example, a wire mesh may be placed betweenthe sections. The re-circulated water inlet 45 is substantiallyseparated from the cool water inlet, the hot water inlet, the steaminlet, and the condensate outlet so that the pre-warming section and there-circulation sections within the tank are similar in volume. Theseparation of the re-circulated water inlet also assists in preventingunnecessary heating of the condensate.

In the example illustrated in FIGS. 11 and 12, the water flowing throughthe water input line 15 has a temperature of 10° C. and a flow rate of1.9 liters per second. The water leaving the heat exchanger tank throughthe water output line 25 has a temperature of 75° C. and a flow rate of4.1 L/s. The water entering the heat exchanger tank from there-circulation line 35 has a flow rate of 2.2 L/s and the temperature ofthe water close to the re-circulated water inlet has a temperature of72° C. The temperature of the steam entering the tank through the steaminput line is 250° C., and the condensate leaving the tank has anaverage temperature of 60° C.

FIGS. 13-16 illustrate cross-sectional views of heat exchange tankswhere the steam within the tank travels through a plurality ofhorizontal plates 155 before leaving through the condensate outlet 65.The plates are structured so that the incoming and outgoing watercirculates around the plates. The illustrated plates are horizontallyoriented such that they do not substantially inhibit the horizontalcirculation of the water while limiting the vertical water circulation.Limiting the vertical flow of water helps to maintain the pre-warmingsection of the tank at a lower temperature than the re-circulationsection which improves the efficiency of the heat transfer. In theillustrated example, the water flowing through the water input line 15has a temperature of 300 K and a flow rate of 2.0 liters per second. Thewater leaving the heat exchanger tank through the water output line 25has a temperature of 350 K and a flow rate of 6.0 L/s. The waterentering the heat exchanger tank from the re-circulation line 35 has aflow rate of 4.0 L/s and the temperature of the water close to there-circulated water inlet has a temperature of 345 K. The temperature ofthe steam entering the tank through the steam input line is 525 K, andthe condensate leaving the tank has an average temperature of 360 K.

FIGS. 17 and 18 illustrate an example of a brazed plate style heatexchanger where the steam and water flow in opposite directions onalternating levels 160 formed by the brazed plates. The brazed platesmay have a non-smooth surface 165 adapted to increase the turbulence ofthe water and steam/steam condensate to thereby improve the efficiencyof the heat transfer.

Although the heat exchanger system has been described in regards toheating water, the heat exchanger can also be used for radiant heatingsystems. In those instances, the fluid being warmed may include amountsof other substances such as glycol, sodium titrate, NOBURST® HydronicSystem Cleaner, E-3 Defoaming Agent, and INHIBITOR BOOST. Otherchemicals may also be added to the fluid to inhibit corrosion, preventfreezing, increase the boiling point of the fluid, inhibit the growth ofmold and bacteria, and allow for improved leak detection (for example,dyes that fluoresce under ultraviolet light). Based on the fluid beingwarmed, the heat exchanger tank may be structured accordingly. Forexample, the pre-warming and re-circulation sections of the heatexchanger may be lined with a protective film if the warmed fluid issomewhat corrosive.

While the principles of the invention have been shown and described inconnection with specific embodiments, it is to be understood that suchembodiments are by way of example and are not limiting. Consequently,variations and modifications commensurate with the above teachings, andwith the skill and knowledge of the relevant art, are within the scopeof the present invention. The embodiments described herein are intendedto illustrate best modes known of practicing the invention and to enableothers skilled in the art to utilize the invention in such, or otherembodiments and with various modifications required by the particularapplication(s) or use(s) of the present invention. It is intended thatthe appended claims be construed to include alternative embodiments tothe extent permitted by the prior art.

1. A thermal energy transfer system for transferring heat energy betweena first fluid and a second fluid, the system comprising: a first fluidcircuit; a second fluid circuit; a heat exchanger containing portions ofboth the first fluid circuit and the second fluid circuit, wherein thecontained portions are in adjacent, thermally-conductive contact forfacilitating heat transfer between the second fluid and the first fluid,wherein the heat exchanger is floodable in a determined proportionwithin a flooded one of the contained portions of the first and secondfluid circuits; a control valve downstream of the flooded one of thecontained portion, the control valve configured to control a fluid flowrate through heat exchanger and selectively calibrate the proportion ofthe heat exchanger that is flooded within the flooded one of thecontained portions; and a stabilization loop having a first inlet linkedto the first fluid circuit downstream of the heat exchanger, an outletlinked to the first fluid circuit at or upstream of the heat exchanger,and a storage tank fluidly linked between the first inlet and theoutlet.
 2. The system of claim 1 further comprising a second inlet ofthe stabilization loop linked to the first fluid circuit, a portion ofthe first fluid flowing directly from the second inlet of thestabilization loop to the storage tank.
 3. The system of claim 2 whereinthe first fluid circuit includes a sub-circuit, apart from thestabilization loop, from the second inlet of the stabilization loop tothe outlet of the stabilization loop.
 4. The system of claim 3 whereinthe sub-circuit includes a diverter valve for attenuating the flow ofthe first fluid through the sub-circuit.
 5. The system of claim 2further comprising a bypass line secured to both the second inlet of thestabilization loop and the storage tank for transporting first fluiddirectly from the second inlet of the stabilization loop to the storagetank.
 6. The system of claim 5 further comprising the first fluidcircuit includes a sub-circuit, apart from the stabilization loop, fromthe second inlet of the stabilization loop to the outlet of thestabilization loop, the sub-circuit includes a diverter valve forattenuating the flow of the first fluid through the sub-circuit, and thestabilization loop further includes a variable flow rate pump forpumping the first fluid from the first inlet of the stabilization loopto the outlet of the stabilization loop.
 7. The system of claim 1wherein the stabilization loop includes a variable flow rate pump forpumping the first fluid from the first inlet of the stabilization loopto the outlet of the stabilization loop.
 8. The system of claim 1further comprising a shutoff valve for the second fluid between theinlet of the second fluid circuit and the heat exchanger for selectivelystopping the flow of second fluid into the heat exchanger and forming alow-pressure region within the heat exchanger; and the second fluidcircuit further includes a reverse flow mechanism configured to allowthe second fluid to be drawn back into the heat exchanger unit towardsthe low-pressure region.
 9. The system of claim 1 wherein the heatexchanger includes a plurality of condensate tubes.
 10. The system ofclaim 1 further comprising a line extending between the first inlet ofthe stabilization loop and the storage tank for transporting first fluidfrom the first inlet of the stabilization loop to the storage tank, anda tank outlet line secured to both the outlet of the stabilization loopand the storage tank for transporting a pre-warmed first fluid from thestorage tank to the outlet of the stabilization loop.
 11. A stabilizedheat exchange system with a first fluid and a second fluid leaving theheat exchange system, the system comprising: a heat exchanger configuredto have the first and second fluids in adjacent, thermally-conductivecontact facilitating heat transfer from the second fluid to the firstfluid to warm the first fluid from a warm temperature when entering theheat exchanger to a hot temperature, that is greater than the warmtemperature, when exiting the heat exchanger; the heat exchangerconfigured to condense the second fluid from a gas to a liquid, whereinthe relative proportions of the gas and the liquid within the heatexchanger are regulated by a fluid control valve; the fluid controlvalve located downstream of the heat exchanger in the flow of the secondfluid, the fluid control valve configured to control the flow rate ofthe second fluid; and a circuit with a first junction where the portionof first fluid is admixed with first fluid having a cool temperaturethat is less than the warm temperature, a second junction, separate fromthe first junction, where the portion of first fluid is again admixedwith the first fluid having the cool temperature, wherein a portion ofthe first fluid in the circuit flows from the heat exchanger with thehot temperature to the first junction to the second function to the heatexchanger where the portion of the first fluid enters the heat exchangerwith the warm temperature.
 12. The system of claim 11 further comprisinga first fluid inlet providing the first fluid at the cool temperature, afirst cool fluid path extending from the first fluid inlet to the firstjunction, and a second cool fluid path extending from the first fluidinlet to the second junction.
 13. The system of claim 12 furthercomprising a diverter valve in the second cool fluid path restrictingthe flow of the first fluid through the second cool fluid path anddiverting the first fluid to the storage tank via the first cool fluidpath.
 14. The system of claim 11 further comprising a variable flow ratepump pumping the portion of first fluid exiting the heat exchanger withthe hot temperature to a storage tank.
 15. The system of claim 11wherein the first junction is located distant from the second junction.16. A method of heating a first fluid with a second fluid within a heatexchange system, the method comprising the steps of: circulating thefirst fluid through a first fluid circuit with a flooded section in aheat exchanger; circulating the second fluid through a second fluidcircuit with a condensing section of the heat exchanger, wherein withinthe heat exchanger the first and second fluid circuits are in adjacent,thermally-conductive contact whereby heat from the second fluid istransferred to the first fluid; condensing the second fluid within theflooded heat exchanger to form a condensate within the heat exchanger;adjusting the flow rate of the second fluid through the heat exchangerto vary the volume of the condensate in the condensing section;stabilizing the temperature of the first fluid leaving the heatexchanger by recirculating a portion of the first fluid from downstreamof the heat exchanger to a pre-heating storage tank where therecirculated portion of the first fluid mixes with a cold first fluidfrom upstream of the heat exchanger, flowing the recirculated portion ofthe first fluid to a second junction where the recirculated portion ofthe first fluid again mixes with the cold first fluid from upstream ofthe heat exchanger, and then flowing the recirculated portion of thefirst fluid to the heat exchanger.
 17. The method of claim 16 furthercomprising diverting a first portion of the cold first fluid from thesection junction to the pre-heating storage tank with a diverter valve.18. The method of claim 16 further comprising pumping, with a variablespeed pump, the recirculated portion to the pre-heating storage tank.19. The method of claim 16 further comprising diverting a first portionof the cold first fluid from the section junction to the pre-heatingstorage tank with a diverter valve.